mailman is vulnerable to cross-site scripting (XSS) attacks. The vulnerability exists as the web UI in Mailman before 2.1.26 allows remote attackers to inject arbitrary web script or HTML via a user-options URL.
packetstormsecurity.com/files/159761/Mailman-2.1.23-Cross-Site-Scripting.html
www.securityfocus.com/bid/104594
access.redhat.com/errata/RHSA-2018:0504
access.redhat.com/errata/RHSA-2018:0505
access.redhat.com/security/updates/classification/#moderate
bugs.launchpad.net/mailman/+bug/1747209
lists.debian.org/debian-lts-announce/2018/02/msg00007.html
usn.ubuntu.com/3563-1/
www.debian.org/security/2018/dsa-4108
www.mail-archive.com/[email protected]/msg70375.html